1. Field of the Invention
The present invention relates to the step of further contracting a contact hole size called thermal flow which is heat treatment for a contact hole pattern in the formation of contact holes. More specifically, the present invention relates to ultra fine contact hole forming methods for adjustably varying the amount of a stable organic compound which does not react with the various components of the resist material and which does not alter a resolution property. It can circumvent the problems of post thermal flow contact hole size fluctuations and fluctuations in contraction size and flow amount which occur despite heating at identical temperatures when the resist material lots change. Thus, easy process control of the manufacture of ultra LSI can be attained.
2. Description of the Related Art
Recently developed acid-catalyzed chemical amplification positive resist materials (Japanese Patent Publication (JP-B) No. 2-27660/1990 and Japanese Patent Provisional Publication (JP-A) No. 63-27829/1988 for example) hold particular promise as a resist material having high sensitivity, resolution and resistance to dry etching and excellent properties, especially suitable for far ultraviolet lithography, using high luminescence KrF excimer lasers or ArF excimer lasers as a far ultraviolet light source.
Such chemical amplification positive resist materials are known in dual component systems comprising a base resin and an acid generator, and triple component systems comprising a base resin, an acid generator and a dissolution controlling agent having an acid-labile group.
For example, Japanese Patent Provisional Publication (JP-A) No. 62-115440/1987 proposes a resist material comprising poly-4-tert-butoxystyrene and an acid generator, and similarly Japanese Patent Provisional Publication (JP-A) No. 3-223858/1991 proposes a dual component system resist material comprising a resin having a tert-butoxy group and an acid generator. Further, Japanese Patent Provisional Publication (JP-A) No. 4-211258/1992 proposes a dual component system resist material comprising a polyhydroxystyrene having a methyl, isopropyl, tert-butyl, tetrahydropyranyl or trimethylsilyl group, and an acid generator.
Still further, Japanese Patent Provisional Publication (JP-A) No. 6-100488/1994 proposes a resist material comprising a polydihydroxystyrene derivative such as poly[3,4-bis(2-tetrahydroxypyranyloxy)styrene], poly[3,4-bis(tert-butoxycarbonyloxy)styrene] or poly[3,5-bis(2-tetrahydropyranyloxy)styrene], and an acid generator.
The improvement and development of the resist resin of those resist materials have advanced. According to Japanese Patent Provisional Publication (JP-A) No. 10-207066/1998, a resist material is proposed which imparts a high contrast and a high resolution, by cross-linking a base resin with a cross-linking group containing a C—O—C group and detaching the cross-linking group by the acid generated after exposing the acid generator to light.
However, even using these chemical amplification positive resist materials having such increased resolving power, it is difficult to realize a contact hole size with a diameter of no more than 0.20 μm, and a resist material for forming a contact hole pattern satisfying the demands of the next generation LSI devices is difficult to find.
On the other hand, there is a contact hole size contraction method (this process technology is noted below as “thermal flow”) known as a process technology for forming contact hole sizes of no greater than 0.2 μm by heating the contact hole pattern so as to fluidize a resist film. By using this thermal flow technology, it is possible to form ultra fine contact hole sizes of 0.10 μm or 0.15 μm.